diff --git a/lib/net/http_fetch_plugin.js b/lib/net/http_fetch_plugin.js
index 806a9c54f4..f6e76aa3f6 100644
--- a/lib/net/http_fetch_plugin.js
+++ b/lib/net/http_fetch_plugin.js
@@ -109,7 +109,7 @@ shaka.net.HttpFetchPlugin = class {
     const fetch = shaka.net.HttpFetchPlugin.fetch_;
     const ReadableStream = shaka.net.HttpFetchPlugin.ReadableStream_;
     let response;
-    let arrayBuffer;
+    let arrayBuffer = new ArrayBuffer(0);
     let loaded = 0;
     let lastLoaded = 0;
 
diff --git a/lib/net/http_plugin_utils.js b/lib/net/http_plugin_utils.js
index ec8043d684..cf4f23d580 100644
--- a/lib/net/http_plugin_utils.js
+++ b/lib/net/http_plugin_utils.js
@@ -6,6 +6,7 @@
 
 goog.provide('shaka.net.HttpPluginUtils');
 
+goog.require('goog.asserts');
 goog.require('shaka.log');
 goog.require('shaka.util.Error');
 goog.require('shaka.util.StringUtils');
@@ -27,6 +28,8 @@ shaka.net.HttpPluginUtils = class {
    * @return {!shaka.extern.Response}
    */
   static makeResponse(headers, data, status, uri, responseURL, requestType) {
+    goog.asserts.assert(data, 'Data should be non-null!');
+
     if (status >= 200 && status <= 299 && status != 202) {
       // Most 2xx HTTP codes are success cases.
       /** @type {shaka.extern.Response} */